Home Forums Hunting & Shooting Hunting Optics Scope adjustments, how much is too much?

For the gurus here:

It is pretty well accepted that scopes work best when near the center of their adjustment range. This begs the question of “How much adjustment is too much?” More specifically, “How much adjustment are you willing to tolerate before you consider adjustable mounts?”

Let us make the following assumptions:
- We are talking about “set and forget”, not ranging and adjusting.
- We assume too much adjustment is a combination of windage and elevation, specifically (following the Pythagorean Theorem):
Total Adjustment = Square root (windage^2 + elevation^2)
- We will say “too much” is some percentage of the total adjustment in either windage or elevation (which are usually the same, or at least close.)

Example: Elevation and windage adjustment range are both 52 MOA. We center the scope and find that to zero requires “12 MOA up and 8 MOA left.” This works out to:
Square root (12^2 + 8^2) = 14.4 MOA
14.4 = 27.7% of 52 (because 14.4 / 52 = 0.277)

So, how much is too much, 25%, 50%, 75% . . . what is your number?

Note: Assuming 52 MOA is the total adjustment up/down, right/left, we have only one half that amount from center, or 26 MOA. This means that in our example we have used 55.4% of the available adjustment (14.4 / 26 = 0.554). Either one works all long as everyone understands and agrees what the percentage is based on.

For our discussion, let us use the total adjustment range, i.e. 52 MOA in our example.

With a top quality s one it should not be a big deal in my opinion. If the scope has the adjustment then you should be able to use the amount needed without having to spend more money. On correction to get the scope closer to center so it will function properly.

Thanks for the reply jwp475.

Based on the lack of response, apparently people say trying to keep a scope near center is a good thing, but not many actually pay much attention to it?
Either that or I confused the question too much with too much math. Since some scopes have so much more adjustment than others, a percentage number was the only thing that made sense to me.

IME a well-designed scope is very insensitive to erector position, in both image quality and erector function, but some of the poorer designs have had considerable image degradation when the erector is moved away from center by any more than about 15% of its total travel.

I don’t know the answer, but I’d just start with it centered and run the dials towards the edge and while viewing a challenging scene, see if I could tell a difference with a given scope.

I have Swarovski PH. 6-24x50 headed back from a check up. Bought the scope new in 1997. Zero used up almost all the windage adjustments. Scope was mounted in Talley rings. Swarovski tech told me the internals set in springs. Best to be centered. Hasbeen

Just to clarify, so you mean about 30% of the available travel from center (1/2 the total travel)?

Correct, roughly +/- 15%

I think we are talking two different things.
Let's say a scope has a total of 50 MOA in both windage and elevation. I'm pretty sure we both understand that this means you can move about 25 MOA from center in any direction (combination of windage and elevation.)
Are you suggesting to stay within 0.15 x 25 = 3.75 MOA from center or 0.30 x 25 = 7.5 MOA from center?

Sorry for any confusion in how I asked for clarification.

This may have been true 20 years ago.

If I have a scope that I need to worry about the elevation or windage turrets being centered for it to work correctly or get the best out of that scope it’d be time to go shopping for one that doesn’t require it...

If a scope is advertised at 50 MOA of total travel then I best be able to use all 50 MOA without any comprises what so ever...

I haven't specifically tested windage, so my comments are mainly based on elevation travel. The worst scope designs that I have tested, for example, may have a total of 30 MRAD of elevation travel in the erector, but I start to notice optical degradation when adjusted any more than about 5 MRAD from center- so +/- 5 MRAD from center.

+1

I use Burris Signature rings with inserts to make the "external" scope adjustments first when sighting in a rifle (getting the impact point to within 5 inches or so from the point I'm aiming at), then fine tune the scope to get it where I want it. The Signature rings work great.

^^^^^^^
I'm a fan of the Burris Signature rings as well, specifically the Signature Zee rings. They have other advantages in addition to the offset inserts to center a scope. My only real complaint is that they sometimes don't mount the scope as low as other rings. So I sometimes don't use them unless I need the centering feature, and that was the purpose of my original post, i.e. when is enough adjustment required that one should consider adjustable mounts?

I do not know how scope function is manipulated internally.

With that disclaimer I am in agreement with those that think in the middle or close is a happy spot. So many rules of thumb in industry advise. Gas or liquid pressure gauges are said to be the most accurate in the middle, if system pressure is normal @ 500 psi, use a 1000 psi gauge. Apples & plums maybe, but from just strictly a mechanical viewpoint, it makes sense.

How would you want the shock absorber normally positioned on your car?



Just pondering.

With instrumentation you pick a range twice the normal setting so that you get useful info for any excursions.

With springs I think the concern was that they lose effectiveness if compressed for a long time - shouldn't be an issue these days with a proper design and materials.